
80C186EC188EC 80L186EC188EC
Table 2 Pin Descriptions
(Continued)
Pin Name
Pin
Input
Output
Pin Description
Type
States
RD
O
H(Z)
ReaD
output signals that the accessed memory or IO
device should drive data information onto the data bus
R(Z)
I(1)
P(1)
WR
O
H(Z)
WRite
output signals that data available on the data bus are
to be written into the accessed memory or IO device
R(Z)
I(1)
P(1)
READY
I
A(L)
READY
input to signal the completion of a bus cycle READY
must be active to terminate any 80C186EC bus cycle unless
S(L)
it is ignored by correctly programming the Chip-Select unit
(Note 1)
DEN
O
H(Z)
Data ENable
output to control the enable of bi-directional
transceivers in a buffered system DEN is active only when
R(Z)
data is to be transferred on the bus
I(1)
P(1)
DTR
O
H(Z)
Data TransmitReceive
output controls the direction of a bi-
directional buffer in a buffered system
R(Z)
I(X)
P(X)
LOCK
IO
A(L)
H(Z)
LOCK
output indicates that the bus cycle in progress is not
interruptable The processor will not service other bus
R(Z)
requests (such as HOLD) while LOCK is active This pin is
I(X)
configured as a weakly held high input while RESIN is active
P(X)
and must not be driven low
HOLD
I
A(L)
HOLD
request input to signal that an external bus master
wishes to gain control of the local bus The processor will
relinquish control of the local bus between instruction
boundaries that are not LOCKed
HLDA
O
H(1)
HoLD Acknowledge
output to indicate that the processor
has relinquished control of the local bus When HLDA is
R(0)
asserted the processor will (or has) floated its data bus and
I(0)
control signals allowing another bus master to drive the
P(0)
signals directly
NCS
O
H(1)
Numerics Coprocessor Select
output is generated when
acessing a numerics coprocessor This signal does not exist
R(1)
on the 80C188EC80L188EC
I(1)
P(1)
ERROR
I
A(L)
ERROR
input that indicates the last numerics processor
extension operation resulted in an exception condition An
interrupt TYPE 16 is generated if ERROR is sampled active
at the beginning of a numerics operation Systems not using
an 80C187 must tie ERROR to VCC This signal does not
exist on the 80C188EC80L188EC
NOTE
Pin names in parentheses apply to the 80C188EC80L188EC
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